1. Field of the Invention
The present invention relates to proximity switches or detectors and more particularly to electronic controlled devices of this type sensitive to the presence of a person or object in its vicinity.
2. Brief Description of the Prior Art
In the past, a variety of proximity detectors and switches have been employed which respond to the presence of an object or agent. Problems and difficulties have been encountered with these prior devices such as disclosed in U.S. Pat. Nos. 3,384,789 and 2,810,066 which stem largely from the fact that mechanical relys are employed. Such relys are noisy and have a tendancy to foul easily. Also, these latter devices are electro-mechanical and are therefore heavy and require mechanical maintenance.
Therefore, a long standing need has existed to provide a novel proximity detector or switch which is composed entirely of electronic components and which is not sensitive to spurious line voltages or other interferences.